Minimizing Battery Stress during Hybrid Electric Vehicle Control Design: Real World Considerations for Model-Based Control Development

In a mild hybrid electric vehicle (HEV) aggressive use of the electrical powertrain is desired to maximize the benefits from hybridizing the vehicle, however this has negative consequences for battery management, battery state of health, and motor temperature. In this paper a control strategy cost function is presented which can minimize these negative effects without significantly affecting the achievable reduction in fuel consumption, and without requiring a detailed battery model or a motor thermal model. This concept is demonstrated on a retrofit HEV unit developed by Ashwoods Automotive, with a model validated using chassis dynamometer test data. Dynamic Programming (DP) is used to optimize the controller, and some limitations of DP which are not often recognized are discussed.